With the ability to embed within the human body a fuel cell that runs on glucose, the same fuel that the rest of our body runs on, we gain an amazing range of new functionality. Starting with a simple list of implantable devices that exist today (insulin pumps, pacemakers), this will expand to eventually include bio-sensors for medical evaluation, artificial organs, advanced prosthetics and cyborg enhancements of human functions.

Scientists have implanted the first functional glucose biofuel cell in a living animal. Unlike batteries that supply power to implants, a power-generating device may not have to be surgically removed and replaced, because glucose is a potentially limitless source of energy.

The device uses enzymes to harvest energy from glucose and oxygen found naturally in the body. Past attempts at using such a device in animals have failed because the enzymes have required acidic conditions or were inhibited by charged particles in the fluid surrounding cells. But Philippe Cinquin and his team from Joseph Fourier University in Grenoble, France, overcame these obstacles by confining selected enzymes inside graphite discs that were placed into dialysis bags. Glucose and oxygen flowed into the device, but enzymes stayed in place and catalyzed the oxidation of glucose to generate electrical energy.

The most potent sugar-powered fuel cells to date, so-called glucose biofuel cells, rely on enzymes that harvest electricity from chemical reactions—for instance, the combination of glucose with oxygen, both available in the human (and rat) body. Compounds dubbed “redox mediators” then act like wires, transporting electric charge from these enzymes to electrodes that lead from the fuel cell to whatever device it is powering. Scientists are currently pursuing a variety of such devices to generate electricity in an environmentally friendly manner.

Unfortunately, the enzymes used in past glucose biofuel cells were not suitable for implants, because they either required highly acidic conditions to work or were inhibited by a variety of ions found in the body. The newly developed devices lack these constraints and are the first functional implantable glucose biofuel cells, with prototypes in rats stably generating power for at least three months.